Digital Manufacturing

UV curable photopolymers

"Cross-linked", so they don't melt, less creep, less stress relaxation; often acrylate and epoxy-based resins

CNC code rules

% starts, then program umber, then safety codes, then stock defn, then tool change, then move to position, etc

Generalized AM process chain (8 steps)

1) CAD; 2) Conversion to STL; 3) Transfer to AM machine and STL manipulation; 4) Machine setup; 5)Build; 6) Removal; 7) Post-processing 8) Application

The characteristics of a digital twin include

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Stereolithography

A rapid prototyping process that fabricates a part layer-wise by hardening a photopolymer with a guided laser beam.

Define ductility

Ability to withstand tension

Selective Laser Sintering (SLS)

An additive manufacturing technique that uses a laser to fuse small particles of material into a mass that has a desired 3D shape.

Canned cycle for G code does what?

Avoids coding for repeating tasks

Expression for engineering strain

Change in L/initial L (does not take into account changing x-section)

CAD

Computer Aided Design

CAE

Computer Aided Engineering

CAM

Computer Aided Manufacturing

CAPP

Computer Aided Process Planning

CAQ

Computer Aided Quality Assurance

CIM

Computer Integrated Manufacturing. A company-wide management philosophy for planning, integration, and implementation of automation.

Cd

Cure depth (for photopolymerization)

Dynamic analysis large problems

Determinant search to get near a root; vector iteration to get eigenvector and value; transformation method to orthogonalize iteration vectors; sturm sequence method to make sure required eigenvalues have been calculated (will make sure number of eigenvalues is right)

Advantages of powder based fusion

Don't need support, more complex geometries possible, wide range of materials can be made

Work curve for photopolymerization: Dp = ?

Dp = depth of penetration of laser into a resin

Work curve for photopolymerization: Ec = ?

Ec = critical exposure at which resin solidification starts to occur

ERP

Enterprise Resource Planning

Governing equations to solve plastic deformation

Equilibrium equations; yield criterion; constitutive equations; compatibility conditions

Physics of Injection molding

Filling (Characterize by high flow rates and high shear rate; convection is the dominant heat transfer mechanism); packing (low flow rates, conduction is dominant heat transfer mechanism); cooling

Full melting AM

For powder bed fusion processing of engineering metal alloys; entire region of material is melted below layer thickness

Part growth phenomenon

For selective laser sintering; powder that's not supposed to bind does

Two photon VP

High resolution, point by point;uses intersection of two scanning laser beams; fabrication occurs below resin surface

Epoxy based resin is sensitive to?

Humidity

Selective laser sintering process

Infrared heaters keep forming part/unused powder warm; focused CO2 laser beam is moved around bed

Control of extrusion is based on what 6 things?

Input pressure; temperature; nozzle diameter; material characteristics; gravity and other factors; temp build up within part

Flow stress equation = K*epsilon^n*epsilon^m; K = ?, n = ?, m = ?

K = material strength coefficient; n = strain hardening exponent; m = strain rate sensitivity exponent

Mask Projection VP

Large radiation beam, patterned by another device: digital micromirror device; requires new layer of resin

Vector scan VP

Laser goes through optics, and then "scanning galvanometers" to mirror onto vat; requires resin recoating

Yield criteria

Limit of elasticity before plastic deformation

Injection molding facts

Lowest possible hold pressure should be used for semi-crystalline plastics during the packaging phase to give higher crystallinity; higher temp results in better surface gloss; mechanical strength of semi-crystalline plastics is not influenced by crystallinity

Physics of Casting

Mass continuity; mernoulli's principle; laminar and turbulence flow; solidification/heat transfer

Components of DM (6 things)

Modeling, simulation, visualization, data analytics, mafuafturing,

Engineering vs true stress

On stress-strain diagram, engineering curves down faster after yield point

Information from FEA

Packages: ANSYS, DEFORM

4 most dominant factors affecting surface roughness

Part orientation; layer thickness; resin properties; building style

3 parts of digital twin

Physical and virtual product; connected data

Liquid phase sintering

Portion of particles melt, other parts stay solid

Role of analysis in Forging

Predicting: forging loads; metal flow and final dimensions of part; temps; grain flow and micro-structures; preventing flow induced defects

PPC

Production planning and control

Characteristics of digital twin (3)

Real-time reflection; interaction; self-evolution

Four drivers of paradigm shift from conventional to digital manufacturing

Rise in data volumes, computational power, connectivity; analytics and business-intelligence capabilities; improvements in transferring digital instructions to the physical world; new forms of human-machine interactions

Bulk metal forming operations

Rolling; forging; extrusion; drawing

Sheet metal forming operations

Shearing; bending; deep drawing; tube hydroforming

Four types of powder fusion mechanisms

Solid state sintering; chemically induced binding; liquid phase sintering; full melting

T/F: G00 = move tool along shortest path to a programmed x,y,z position

T

In powder based fusion, morphology and size of powders are important because?

The affect powder flowability; influence laser energy absorption; influence thermal conductivity of powder bed

Necking in solid state sintering

The area between spherical particles that is fusing together

Quality of a product produced by metal forming operation can be assessed by?

The max effective strain produced; the effective strain distribution in the part; final dimensions of the part

3 characteristics of powder bed fusion

Thermal sources for inducing fusion between powder particlees; a method for controlling powder fusion to a prescribed region; mechanisms for adding and smoothing powder layers

Why should extrusion based systems have material kept at low temp molten state? (3 reasons)

To avoid degradation of polymers; burned polymer residue may be difficult to remove; a higher temp inside chamber may require additional cooling

T/F: most g words will remain in effect until replaced

True

Chemically induced sintering

Two types of powders or atmospheric gases react

Vat photopolymerization light

UV (usually)

Upfacing vs downfacing surfaces

Upfacing is big zig zag side profiles, down facing is little ones

Flow stress

Value of stress required to keep deforming metal plastically: = K*epsilon^n where K is strength coefficient and n is strain hardening exponent

Extrusion screw thing

Velocity is zero at shaft, increases linearly along outer part

3 common failures in hydroforming

Wrinkling, folding, fracture

Binder jetting

a binder is printed into a powder bed in order to form part cross-sections.

Sheet lamination

deposit a layer of material in sheet form.

Extrusion based AM

deposit a material by extruding it through a nozzle, while scanning the nozzle in a pattern that produces a part cross-section.

the true strain of a material in a compression test can be given by

epsilon = 2ln(D_0/D)

True Strain Equation

epsilon = ln(e + 1)

Strain rate

epsilon dot

Expression for true strain

ln(L/L0)

Avg strain = C*epsilon_dot^m

m = strain rate sensitivity exponent

Powder Bed Fusion

melts fine layers of powderized plastic or metal into solid objects using a laser

Cd vs Emax resin working curve

semilog plot -> straight line

Directed energy deposition

simultaneously deposit a material (usually powder or wire) and provide energy to process that material through a single deposition device.

Vat Photopolymerization

utilize a liquid photopolymer that is contained in a vat and processed by selectively delivering energy to cure specific regions of a part cross-section.